Japanese Patent Laying-Open No. 2010-202012 (PTD 1) discloses minimizing/preventing electric leakage caused when an electric heating catalyst (EHC) is energized. More specifically, the document discloses that when an environmental condition defined by external temperature, humidity, and atmospheric pressure corresponds to a predetermined condensation range, energizing the EHC is started to vaporize moisture, condensed water and the like in exhaust gas.